Wow the Rugby thing is still going on I figured my point about American Football players collisions being talked about as low impact car crashes would be enough.
But ok let's just look at some big misconceptions you have stated.
1) Being that American Football takes less Stamina and because they don't run every minute of every down.
There is a reason for this because in American Football you have to actually sprint and collide every single play of every single down your in. In case you didn't notice there are many times much like in Soccer you can see Rugby players standing around. They still get their breaks as well.
2) That this extra padding amounts to football players being weaker and or wussies.
Once again another misconception because this padding was gradually adapted over long periods of time because of the mounting injuries. Football players are asked to take much harder hits and to hit every play. Rugby is very oriented in the grounds of pushing and dragging tackles. Often times when a person is getting the ball someone is already there and these hard hitting tackles are actually wrap ups where they just drive the guy to the ground. The same kind of tackles 8 year olds make on the playgrounds.
I'm not saying Rugby isn't a very good sport and not fun or not physically demanding but in reality the hits on the body most American Football players take are far worse than the ones Rugby players take.
I can take this from personal knowledge because on the College football team I played for some of the players would quite and join our Rugby team those guys would say the hitting and Football and the hitting in Rugby are different and Football just is harder.